Impairment of transneuronal traffic in Streptozotocin-induced diabetes, a WGA-HRP neurohistochemical study in the rat

Abstract

Retrograde transport of Wheat germ agglutinin conjugated to Horseradish peroxidase (WGA-HRP) was used in labeling vagal neurons projecting to the stomach from the dorsal motor nucleus of the vagus nerve (DMNV) in Streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in the experimental rats by intraperitoneal injection of buffered STZ. Control rats were injected with an equivalent volume of the citrate buffer not containing STZ. The experimental rats, which became diabetic about 24 h after intraperitoneal injection of STZ, were kept alive for a period of 24 weeks to attain a chronic state of diabetes. Control euglycaemic rats were also kept alive for 24 weeks. At the end of 24 weeks, the two groups of rats were prepared for stomach surgery. Following anaesthesia laparotomy was performed and the stomach exteriorized. The anterior and posterior walls of the stomach were injected with 0.1 ml of 5% WGA-HRP in 0.5 M sodium chloride. Experimental and control rats were sacrificed 48-72 h after tracer injection by transcardial perfusion with normal saline, fixative and buffered sucrose. Transverse serial frozen sections of the brainstem were processed for WGA-HRP neurohistochemistry and analyzed under light and dark-field microscopy. The analyses of the sections taken from the chronic diabetic rats revealed fewer WGA-HRP labeled neurons in the DMNV than sections taken from the control euglycaemic rats. The depletion of labeled neurons in the diabetic rats compared with the euglycaemic rats is indicative of an interference with the mechanism of retrograde neuronal transport of WGA-HRP by chronic diabetic state.